The “T”-Rex Block: How is it affecting Kitsap County?

September 19th, 2012 by Matthew Leach

According to the poll I conducted on the right hand side bar,
many of your are eager to read about things pertaining directly to
the Kitsap Peninsula. That’s not too surprising to find, as this
blog is called “Forecasting Kitsap” after all! But I hope you will
forgive me for the lack of coverage of weather events within the
peninsula lately, as summer tends to yield the same weather over
and over again in the Northwest: sunny skies and mild
temperatures.

However, as I was reading a forecast discussion provided by the
National Weather Service in Idaho Falls (I know, that’s random!), I
noticed they used the term “Rex block” in describing our current
weather pattern. I must admit, I wasn’t exactly sure what that was,
so naturally I looked up the definition on the NWS site. Now,
before we talk about the Rex block, let’s discuss what blocking
means in meteorology!

First of all, this term can be broken down through a personal
example: if you encounter a road block on your way to work due to
construction (which probably is hitting home to some of you more
than others!) what options are given to you? Usually if the project
is wide-scale enough, they’ll provide a detour. Such is the case in
weather. Sometimes “road blocks” are set up in the atmosphere and
this will usually cause the jet stream to take a detour. Here’s an
example:

This is called an “omega block”, primarily because of its shape
of the jet stream: Ω. As you can see from the picture, a ridge of
high pressure built in the interior west and forced all our
would-be active weather up and over our region and sliding it down
into the northeast. This is definitely not an uncommon pattern
during El Nino years! We get a handful of these “omega” blocks,
and…well, my personal bias is…they’re not fun!

So, if you haven’t given up reading by now, let’s take a look at
the Rex block, named after the meteorologist who discovered the
pattern. I call it the “T”-Rex block for three reasons: 1) it’s
stubborn, 2) it can be aggressive (for those on the other end of
the block!) and 3) it eventually goes extinct. So, with that
horrifying blood-thirsty monster firmly planted in our minds, let’s
look at its counterpart in weather:

Very often in a Rex block scenario, an area of high pressure is
situated to the very north of an area of low pressure, and air flow
tends to move very slowly during this process which can mean the
same type of weather for weeks at a time. Take a look at this
weather chart that depicts where we are right now:

**Note: Commenter Donna noticed an actual shape of a
dinosaur right over the coast! Do you see the curved head and large
nose over the Canadian coastline into the Pacific? Thanks, Donna,
for pointing that out!**

The area of high pressure (signaled by a small “H” along the
coast of western Canada) is directly north of an area of low
pressure (situated southwest of LA). This of course is the reason
why we’ve been stuck on repeat the past several weeks and the
northeast has been so chilly!

And it looks like this block will remain stubborn for at least
the next week or so. Aside from areas of morning clouds/fog over
the next couple of days, we’ll remain largely pleasant with
seasonable highs in the upper 60s/low 70s under partly sunny skies.
It also looks like we’re still on for a pattern change within the
first few days of October.

So the next time you have to take a detour, just think of good
ol’ Rex!

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on Wednesday, September 19th, 2012 at 3:37 pm by Matthew Leach and is filed under Uncategorized.
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3 Responses to “The “T”-Rex Block: How is it affecting Kitsap County?”

Thanks for the lesson. Exactly what I was looking for when I took the poll. I was also taken by the vagaries of weather forecasting when you mentioned how a typhoon off Japan would be likely to affect the forecast here.

Don’t laugh, while I was studying the map, looking for the ‘h’, my eyes reorganized and I suddenly saw the T-Rex. “Oh, my Gosh, there is a dinosaur!’ Or a dancing dino?, bird? It was only a minor distraction from your interesting post. But did bring a smile.

Ron: I’m glad you enjoyed it! It’s comforting to know I’m not the only one that thinks things like “Rex blocks” are super awesome and fascinating to study! And it is true, many weather factors from Japan, the Gulf of Alaska and even Hawaii effect our weather here! Amazing to think about how complex Pacific Northwest weather really is.

Donna: Thanks for pointing that out! How fun! Here I was talking about dinosaurs, and I missed the very thing on a weather map! Good eye